growth value meaning when summarizing a a model

[Alon Ginatt]

Hello everyone,

This might be a silly question, but I suddenly realized that I'm not sure what the growth value of a model's biomass objective function, upon using model.summary(), actually means. 

basing on https://www.nature.com/articles/nbt.1614 (what is flux balance analysis?), I get that the units of growth of a model are exponential growth hour^-1, but when solving the models, the objective output is:

1.0 growth = X 

This confuses me a bit. If X equals one unit of growth; what does X mean? the growth rate itself? or is it the rate in which metabolites are converted to biomass constituents? if X is the latter, what does a high value of X means?

Thank you all in advance!    

Alon